Mobile communication method, mobile management node, and serving gateway apparatus

ABSTRACT

A mobile communication method in a mobile communication system according to the present invention in which when MME# 1  is restarted in a first state in which a PDN connection # 1  including one or more EPS bearers # 1  is set among a UE, an S-GW# 1,  and a P-GW# 1,  the first state transitions to a second state in which the PDN connection # 1  is released between the UE and the S-GW# 1  and the connection is maintained only between the S-GW# 1  and the P-GW# 1,  the mobile communication method including the step of not transmitting, by the MME# 1, “ Paging” whose destination is the UE upon receiving “DDN” including IMSI of the UE after detecting that re-attach processing for the mobile station has been executed in the second state.

TECHNICAL FIELD

The present invention relates to a mobile communication method, a mobilemanagement node, and a serving gateway apparatus.

BACKGROUND ART

In a mobile communication system of an EPS (Evolved Packet System) typespecified in 3GPP, there is proposed an operation to be carried out whena P-GW (Packet Data Network-Gateway, packet data network gatewayapparatus) #1 receives user data whose destination is a UE (UserEquipment) in an idle state under control of an MME (Mobility ManagementEntity, mobile management node) #1, after the MME#1 which has beensuspended due to a failure or the like is restarted.

The operation will be described below with reference to FIG. 4.

As shown in FIG. 4, when the MME#1 is restarted in step S3001 in a state(first state) in which a PDN connection #1 including one or more EPSbearers #1 is set among the UE, an S-GW (Serving Gateway, servinggateway apparatus) #1, and the P-GW#1, the state transitions to a state(second state) in which the PDN connection #1 is released between the UEand the S-GW#1 and the PDN connection #1 is maintained only between theS-GW#1 and the P-GW#1.

In step S3002, upon receiving user data whose destination is the UE onthe EPS bearer #1 from an external network, the P-GW#1 transmits theuser data whose destination is the UE to the S-GW#1 through the EPSbearer #1 in step S3003.

In step S3004, the S-GW#1 transmits “DDN (Downlink Data Notification,downlink notification signal)” to the MME#1, because the PDN connection#1 is released between the UE and the S-GW#1.

In step S3005, upon receiving the “DDN”, the MME#1 transmits “Paging”whose destination is the UE specified by “IMSI (International MobileSubscriber Identity)” included in the “DDN”.

In step S3006, upon receiving the “Paging” whose destination is the UE,the UE transmits “Attach Request (attach request signal)” to a corenetwork so as to start re-attach processing. The “Attach Request” istransferred to an MME#2 via a radio access network.

In step S3007, the MME#2 performs location registration processing forthe UE with an HSS (Home Subscriber Server, subscriber informationserver apparatus).

In step S3008, a PDN connection #2 including one or more EPS bearers #2is set among the UE, an S-GW#2, and a P-GW#2.

In step S3009, the MME#2 transmits “Attach Accept” to the UE.

CITATION LIST Non Patent Literature

[Non Patent Literature 1] 3GPP TR23.857

SUMMARY OF INVENTION Technical Problem

However, in the example of FIG. 4, when the P-GW#1 receives the userdata whose destination is the UE on the EPS bearer #1 from the externalnetwork in step S3010, the following problem occurs.

That is, in step S3011, the P-GW#1 transmits the user data whosedestination is the UE to the S-GW#1 through the EPS bearer #1, and instep S3012, the S-GW#1 transmits, in a similar manner as step S3004, the“DDN” in which the IMSI is set to the MME #1 because the PDN connection#1 is released between the UE and the S-GW#1.

As a result, in step S3013, upon receiving the “DDN”, the MME#1transmits the “Paging” whose destination is the UE specified by the

“IMSI” included in the “DDN”, thereby consuming unnecessary radioresources while causing a communication disconnect in step S3014.

Alternatively, when the MME#1 holds S-TMSI or the like in a memory, the“Paging” whose destination is to the UE specified by the S-TMSI in placeof the IMSI may be transmitted. In this case, transmission of the“Paging” in step S3013 consumes unnecessary radio resources.

Accordingly, the present invention has been made in view of theabove-mentioned problem, and an object of the present invention is toprovide a mobile communication method, a mobile management node, and aserving gateway apparatus which are capable of avoiding transmission ofthe unnecessary paging signal after the MME#1 which has been suspendeddue to a failure or the like is restarted.

Solution to Problem

A first exemplary aspect of the present invention is a mobilecommunication method in a mobile communication system in which when afirst mobile management node is restarted in a first state in which aconnection including one or more bearers is set among a mobile station,a first serving gateway apparatus, and a first packet data networkgateway apparatus, the first state transitions to a second state inwhich the connection is released between the mobile station and thefirst serving gateway apparatus and the connection is maintained onlybetween the first serving gateway apparatus and the first packet datanetwork gateway apparatus, the mobile communication method including thestep of not transmitting, by the first mobile management node, a pagingsignal whose destination is the mobile station upon receiving a downlinkdata notification signal including identification information of themobile station after detecting that re-attach processing for the mobilestation is completed in the second state.

A second exemplary aspect of the present invention is a mobilemanagement node that operates as a first mobile management node for usein a mobile communication system in which when the first mobilemanagement node is restarted in a first state in which a connectionincluding one or more bearers is set among a mobile station, a firstserving gateway apparatus, and a first packet data network gatewayapparatus, the first state transitions to a second state in which theconnection is released between the mobile station and the first servinggateway apparatus and the connection is maintained only between thefirst serving gateway apparatus and the first packet data networkgateway apparatus, the mobile management node being configured not totransmit a paging signal whose destination is the mobile station uponreceiving a downlink data notification signal including identificationinformation of the mobile station after detecting that re-attachprocessing for the mobile station is completed in the second state.

A third exemplary aspect of the present invention is a serving gatewayapparatus that operates as a first serving gateway apparatus in a mobilecommunication system in which when a first mobile management node isrestarted in a first state in which a connection including one or morebearers is set among a mobile station, a first serving gatewayapparatus, and a first packet data network gateway apparatus, the firststate transitions to a second state in which the connection is releasedbetween the mobile station and the first serving gateway apparatus andthe connection is maintained only between the first serving gatewayapparatus and the first packet data network gateway apparatus, theserving gateway apparatus being configured to release the connectionupon, in the second state, transmitting to the first mobile managementnode a downlink data notification signal including identificationinformation of the mobile station in response to user data whosedestination is the mobile station received through the bearer and alsoreceiving a response signal for the downlink data notification signalincluding notification information for requesting release of theconnection.

Advantageous Effects of Invention

As described above, according to the present invention, it is possibleto provide a mobile communication method, a mobile management node, anda serving gateway apparatus which are capable of avoiding transmissionof an unnecessary paging signal after the MME#1 which has been suspendeddue to a failure or the like is restarted.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is an overall configuration diagram of a mobile communicationsystem according to a first exemplary embodiment of the presentinvention;

FIG. 2 is a sequence diagram illustrating operation of the mobilecommunication system according to the first exemplary embodiment of thepresent invention;

FIG. 3 is a sequence diagram illustrating operation of a mobilecommunication system according to Modified Example 1 of the presentinvention; and

FIG. 4 is a sequence diagram illustrating operation of a mobilecommunication system of a related art.

DESCRIPTION OF EMBODIMENTS (Mobile Communication System According to aFirst Exemplary Embodiment of the Present Invention)

Referring to FIGS. 1 and 2, a mobile communication system according tothe first exemplary embodiment of the present invention will bedescribed.

As shown in FIG. 1, the mobile communication system according to thisexemplary embodiment includes a P-GW#1, a P-GW#2, an S-GW#1, an S-GW#2,an MME#1, an MME#2, an E-UTRAN (Evolved Universal Terrestrial RadioAccess Network), and an HSS.

Hereinafter, referring to FIG. 2, description will be made of operationto be carried out when the P-GW#1 receives user data whose destinationis a UE in an idle state under control of the MME#1, after the MME#1which has been suspended due to a failure or the like is restarted inthe mobile communication system according to this exemplary embodiment.

As shown in FIG. 2, when the MME#1 is restarted in step S1001 in a state(first state) in which a PDN connection #1 including one or more EPSbearers #1 is set among the UE, the S-GW#1, and the P-GW#1, the statetransitions to a state (second state) in which the PDN connection #1 isreleased between the UE and the S-GW#1 and the PDN connection #1 ismaintained only between the S-GW#1 and the P-GW#1.

Note that in this case, the S-GW#1 may be set such that only a specificEPS bearer in the PDN connection #1 is not released between the S-GW#1and the P-GW#1.

The EPC bearer may be set the necessity of releasing the EPS bearer inthe S-GW#1 by use of QCI (QoS Class Identifier), a priority type “ARP(Allocation Retention Priority)”, or the like.

Upon receiving user data whose destination is the UE on an EPS bearer #1from an external network in step S1002, the P-GW#1 transmits the userdata whose destination is the UE to the S-GW#1 through the EPS bearer #1in step S1003.

In step S1004, the S-GW#1 transmits the “DDN” including an IMSI of theUE and “EPS Bearer ID#1” which is identification information of the EPSbearer #1 to the MME#1, because the PDN connection #1 is releasedbetween the UE and the S-GW#1 (that is, because restart of the MME#1 isdetected by a GTP echo signal or the like). Note that the “EPS BearerID#1” shall not necessarily be set.

In step S1005, the MME#1 transmits “DDN Ack”, which is a response signalfor “DDN”, to the S-GW#1. Note that the “DDK Ack” shall not necessarilybe transmitted.

In step S1006/S1007, upon receiving the “DDN” in which the IMSI is set,the MME#1 transmits “Paging” whose destination is the UE specified bythe “IMSI” included in the “DDN” while storing information indicatingthe transmission of the “Paging”.

When the MME#1 holds S-TMSI or the like in a memory, the “Paging” whosedestination is the UE specified by the S-TMSI in place of the IMSI maybe transmitted.

In this case, prior to execution of step S1008, the UE transmits“Service Request” to the MME#1, and the MME#1 notifies the UE of areject signal, thereby activating step S1008 which is described later.

In step S1008, upon receiving the “Paging” whose destination is the UE,the UE transmits the “Attach Request” including the IMSI of the UE to acore network so as to start re-attach processing. The “Attach Request”is transferred to the MME#2 via a radio access network.

In step S1009, the MME#2 transmits “Update Location Request” to the HSSso as to start location registration processing for the UE.

In step S1010, the HSS transmits “Cancel Location Request (positionalinformation deletion request signal)” to the MME#1.

In step S1011, the MME#1 detects that the UE re-attached by havingreceived the “Cancel Location Request”.

In step S1012, the MME#1 transmits “Cancel Location Answer” to the HSS.

In step S1013, the HSS transmits “Update Location Request” to the MME#2.

In step S1014, a PDN connection #2 including one or more EPS bearers #2is set among the UE, the S-GW#2, and the P-GW#2.

In step S1015, the MME#2 transmits “Attach Accept” to the UE.

After that, upon receiving the user data whose destination is the UE onthe EPS bearer #1 from the external network in step S1016, the P-GW#1transmits the user data whose destination is the UE to the S-GW#1through the EPS bearer #1 in step S1017.

In step S1018, the S-GW#1 transmits the “DDN” including the IMSI of theUE to the MME#1, in a similar manner as step S1003, because the PDNconnection #1 is released between the UE and the S-GW#1.

Here, since the MME#1 has detected that the UE specified by the “IMSI”included in the “DDN” is already attached, the MME#1 will not transmitthe “Paging” whose destination is the UE.

After that, in step S1019, the MME#1 transmits to the S-GW#1 the “DDNAck” or “DDN Failure” including notification information for requestingrelease of the PDN connection #1 of the UE held between the S-GW#1 andthe P-GW#1.

Here, the MME#1 may include the “EPS Bearer ID#1” in the “DDN Ack” orthe “DDN Failure”. Further, when the MME#1 holds context information(information on the UE), such as the S-TMSI allocated to the UE beforerestart, in the memory, the context information may be deleted.

In step S1020, upon receiving the above-mentioned “notificationinformation”, the S-GW#1 transmits “Delete Session Request” including“Linked Beare ID#1” corresponding to the “IMSI” of the UE to the P-GW#1so as to release the PDN connection #1 which is set between the S-GW#1and the P-GW#1 and which corresponds to the “EPS Bearer ID#1”.

The term “Linked Beare ID#1” herein described refers to identificationinformation for identifying the PDN connection #1.

In step S1021, after the PDN connection #1 is released, the P-GW#1transmits “Delete Session Response” to the S-GW#1.

The mobile communication system according to this exemplary embodimentis configured such that, upon receiving the “Cancel Location Request”for the UE, the MME#1 detects that the UE has re-attached, and afterthat, even upon receiving the “DDN” in which the IMSI is set forinstructing transmission of the “Paging” whose destination is the UE,the MME#1 will not transmit the “Paging” whose destination is the UE.Avoiding transmission of the unnecessary “Paging” in this way enablesavoiding consumption of unnecessary radio resources and generation ofcommunication disconnect.

Modified Example 1

Referring to FIG. 3, a mobile communication system according to ModifiedExample 1 of the present invention will be described below whilefocusing on the differences from the mobile communication systemaccording to the first exemplary embodiment described above.

Hereinafter, referring to FIG. 3, description will be made of operationto be carried out when the P-GW#1 receives user data whose destinationis the UE in the idle state under control of the MME#1, after the MME#1which has been suspended due to a failure or the like is restarted inthe mobile communication system according to Modified Example 1 of thepresent invention.

As shown in FIG. 3, when the MME#1 is restarted in step S2001 in a state(first state) in which the PDN connection #1 including one or more

EPS bearers #1 is set among the UE, the S-GW#1, and the P-GW#1, thestate transitions to a state (second state) in which the PDN connection#1 is released between the UE and the S-GW#1 and the PDN connection #1is maintained only between the S-GW#1 and the P-GW#1.

In step S2002, the UE transmits “Tracking Area Update Request (locationregistration area update request signal)” or “Service Request (servicerequest signal)” to the MME#1.

Upon receiving the “Tracking Area Update Request” or the

“Service Request”, the MME#1 transmits “Tracking Area Update Reject(location registration area reject signal” or “Service Reject (servicereject signal)” to the UE because the MME#1 does not hold the contextinformation of the UE in step S2003.

In step S2004, upon receiving the “Tracking Area Update Request” or the“Service Request”, the UE transmits the “Attach Request” to the MME#2.

The operations in steps S2005 to S2017 are the same as the operations insteps S1009 to S1021 shown in FIG. 2.

Note that the present invention is not limited to the above-describedcases, but can also be applied to the case where the UE transmits the“Attach Request” to the restarted MME#1, upon executing the re-attachprocessing.

That is, in this case, as the MME#1 is aware that the UE isre-connected, upon receiving the “DDN” in which the IMSI of the UE isset, the MME#1 transmits to the S-GW#1 the “DDN Ack” or the “DDNFailure” including the notification information for requesting releaseof the PDN connection #1 held between the S-GW#1 and the P-GW#1.

The aspects of the above-described exemplary embodiments may be alsoexpressed as follows.

A first exemplary aspect of this exemplary embodiment is a mobilecommunication method in a mobile communication system in which when theMME#1 (first mobile management node) is restarted in the first state inwhich the PDN connection #1 (connection) including one or more EPSbearers #1 (bearer) is set among the UE (mobile station), the S-GW#1(first serving gateway apparatus), and the P-GW#1 (first packet datanetwork gateway apparatus), the first state transitions to the secondstate in which the PDN connection #1 is released between the UE and theS-GW#1 and the PDN connection #1 is maintained only between the S-GW#1and the P-GW#1, the mobile communication method including the step ofnot transmitting, by the MME#1, the “Paging (paging signal)” whosedestination is the UE upon receiving the “DDN (downlink datanotification signal)” including the IMSI of the UE (identificationinformation of the mobile station) after detecting that the re-attachprocessing for the UE has been executed in the second state.

The first exemplary aspect of this exemplary embodiment may furtherinclude the steps of: notifying, by the MME#1, the S-GW#1 of nottransmitting the “Paging” when not transmitting the “Paging” whosedestination is the UE; and releasing, by the S-GW#1, the PDN connection#1 (connection) between the S-GW#1 and the P-GW#1 in response to thenotification.

A second exemplary aspect of this exemplary embodiment is an MME thatoperates as the MME#1 in a mobile communication system in which when theMME#1 is restarted in the first state in which the PDN connection #1including one or more EPS bearers #1 is set among the UE, the S-GW#1,and the P-GW#1, the first state transitions to the second state in whichthe PDN connection #1 is released between the UE and the S-GW#1 and thePDN connection #1 is maintained only between the

S-GW#1 and the P-GW#1, the MME being configured not to transmit the“Paging” whose destination is the UE upon receiving the “DDN” includingthe IMSI of the UE after detecting that the re-attach processing for theUE has been executed in the second state.

In the second exemplary aspect of this exemplary embodiment, when theMME does not transmit the “Paging” whose destination is the UE, the MMEmay be configured to notify the S-GW#1 of not transmitting the “Paging”.

A third exemplary aspect of this exemplary embodiment is an S-GW thatoperates as the S-GW#1 in a mobile communication system in which whenthe MME#1 is restarted in the first state in which the PDN connection #1including one or more EPS bearers #1 is set among the UE, the S-GW#1,and the P-GW#1, the first state transitions to the second state in whichthe PDN connection #1 is released between the UE and the S-GW#1 and thePDN connection #1 is maintained only between the S-GW#1 and the P-GW#1,the S-GW being configured to release the PDN connection #1 upon, in thesecond state, transmitting to the MME#1 the “DDN” including the IMSI ofthe UE in response to the user data whose destination is the UE receivedthrough the EPS bearer #1 and also receiving the “DDN Ack” or the “DDNFailure” including the notification information for requesting releaseof the PDN connection #1.

Note that the above-described operations of the MME#1, MME#2, S-GW#1,S-GW#2, P-GW#1, P-GW#2, eNB#1, eNB#2, and UE may be implemented byhardware, a software module executed by a processor, or a combinationthereof.

The software module may be provided in storage media of any form such asRAM (Random Access Memory), flash memory, ROM (Read Only Memory), EPROM(Erasable Programmable ROM), EEPROM (Electronically Erasable andProgrammable ROM), register, hard disk, removable disk, or CD-ROM.

The storage media are connected to the processor so that the processorcan read and write information from and to the storage media. Thestorage media may be integrated in the processor. The storage media andthe processor may be provided in an ASIC. The ASIC may be provided inthe MME#1, MME#2, S-GW#1, S-GW#2, P-GW#1, P-GW#2, eNB#1, eNB#2, and UE.The storage media and the processor may be provided, as discretecomponents, in the MME#1, MME#2, S-GW#1, S-GW#2, P-GW#1, P-GW#2, eNB#1,eNB#2, and UE.

Though the present invention has been described above in detail withreference to the above-described exemplary embodiments, it is apparentto those skilled in the art that the present invention is not limited tothe exemplary embodiments herein described. The present invention can beimplemented as modified and changed modes without departing from thegist and scope of the present invention as defined by the claims.Therefore, the description of the specification is intended forexplaining the example only and does not impose any limited meaning tothe present invention.

REFERENCE SIGNS LIST

-   UE MOBILE STATION-   eNB RADIO BASE STATION-   MME#1, MME#2 MOBILE MANAGEMENT NODE-   S-GW#1, S-GW#2 SERVING GATEWAY APPARATUS-   P-GW#1, P-GW PDN GATEWAY APPARATUS-   HSS SUBSCRIBER INFORMATION MANAGEMENT SERVER

1. A mobile communication method in a mobile communication system inwhich when a first mobile management node is restarted in a first statein which a connection including one or more bearers is set among amobile station, a first serving gateway apparatus, and a first packetdata network gateway apparatus, the first state transitions to a secondstate in which the connection is released between the mobile station andthe first serving gateway apparatus and the connection is maintainedonly between the first serving gateway apparatus and the first packetdata network gateway apparatus, the mobile communication methodcomprising: not transmitting, by the first mobile management node, apaging signal whose destination is the mobile station upon receiving adownlink data notification signal including identification informationof the mobile station after detecting that re-attach processing for themobile station is completed in the second state.
 2. The mobilecommunication method according to claim 1, further comprising:notifying, by the first mobile management node, the first servinggateway apparatus that the re-attaching processing for the mobilestation is completed when not transmitting the paging signal whosedestination is the mobile station; and releasing, by the first servinggateway apparatus, the connection between the first serving gatewayapparatus and the first packet data network gateway apparatus inresponse to the notification.
 3. A mobile management node that operatesas a first mobile management node for use in a mobile communicationsystem in which when the first mobile management node is restarted in afirst state in which a connection including one or more bearers is setamong a mobile station, a first serving gateway apparatus, and a firstpacket data network gateway apparatus, the first state transitions to asecond state in which the connection is released between the mobilestation and the first serving gateway apparatus and the connection ismaintained only between the first serving gateway apparatus and thefirst packet data network gateway apparatus, the mobile management nodebeing configured not to transmit a paging signal whose destination isthe mobile station upon receiving a downlink data notification signalincluding identification information of the mobile station afterdetecting that re-attach processing for the mobile station is completedin the second state.
 4. The mobile management node according to claim 3,wherein the mobile management node is configured to notify the firstserving gateway apparatus that the re-attach processing for the mobilestation is completed when not transmitting the paging signal whosedestination is the mobile station.